Refrigeration Maintenance 10-20
ELECTRONIC THROTTLING VALVE (ETV)
The electronic throttling valve (ETV) is a variable position valve operated by a stepper motor. The ETV is located in the suction
line between the heat exchanger and the accumulator. The ETV controls the flow of refrigerant returning to the compressor.
Therefore, it replaces the modulation valve and compressor throttling valve. During the Full Cool mode, the unit controller sends
an electrical signal to adjust the ETV to maximise system cooling capacity. During the Modulation Cool mode, the unit controller
sends a signal to close the ETV a precise amount. This throttles the suction gas returning to the compressor and reduces the system
cooling capacity to match the load requirements.
Refer to the appropriate Microprocessor Operation and Diagnosis manual for instructions on testing the ETV. Service of the ETV
includes replacement of the stepper motor and piston assembly or the entire valve and body.
HOT GAS BYPASS VALVE
The hot gas bypass valve is used in conjunction with the modulation valve or Electronic Throttling valve to reduce the capacity
of the unit during modulation and also aid suction pressure control. This normally closed solenoid valve is located in the
refrigeration line that connects the discharge line to the hot gas line. The controller energises (opens) the hot gas bypass valve
when the unit reaches full modulation. The controller de-energises (closes) the hot gas bypass valve when the modulation cycle
ends.
For SLXi the hot gas bypass solenoid will pulse during modulation. This is to help reduce fuel consumption.
NOTE: See the appropriate Controller Operation and Diagnosis manual for instructions on testing the hot gas or hot gas
bypass valve.
Electronic Throttling Valve (ETV -
Alco Valve)
Electronic Throttling Valve (ETV -
Danfoss Valve) (prior to August
2016)
Electronic Throttling Valve (ETV -
Danfoss Valve) (after 22nd August
2016)
1. Stepper Motor
2. Valve Body
3. Inlet
4. Outlet
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